1. Field of the Invention
The present invention relates to a mobile communication system enabling connection of a plurality of portable or mobile radio telephone equipment which do not belong to the system to a public network.
2. Description of the Prior Art
FIG. 1 is a system configuration diagram showing a conventional private mobile communication system, hereinafter referred to as a private system. In FIG. 1, reference numeral 1 means a public network to which the mobile communication system is connected, and 2 means a private system. Reference numeral 30 means a private branch exchange (hereinafter referred to as PBX) serving as an exchange for the private system. For example, an electronic exchanging apparatus is employed as the PBX 30. Reference numeral 40 means each radio base station which is accommodated in the PBX 30 and has each predetermined zone, and 50 means a portable or mobile radio telephone equipment which is carried by a user, and is connected to the radio base station 40 by radio, and is also connected to the radio base station 40B directly connected to the public network 1 by radio.
FIG. 2 is a functional block diagram showing a configuration of the portable radio telephone equipment 50. In FIG. 2, reference numeral 11 means a private protocol processing section to process a private protocol of the private system 2, and 12 means a private control channel controlling section to control a private control channel for private protocol transmission. Reference numeral 13 means a public protocol processing section to process a public protocol in relation to the public network 1, and 14 means a public control channel controlling section to control a public control channel for public protocol transmission. Reference numeral 15 means a transmitting/receiving section which is switched over, and is connected to either the private control channel controlling section 12 or the public control channel controlling section 14.
The private protocol processing section 11 connects the portable or mobile radio telephone equipment 50 to the private mobile communication system. The public protocol processing section 13 connects the portable radio telephone equipment 50 to the public network 1. That is, the portable or mobile radio telephone equipment 50 can be connected to both the private communication system and the public network 1.
For example, in case the private communication system is installed in a department store, an employee of the department store can use the portable radio telephone equipment 50 to perform local communication with another employee. Typically, the employee has access to the public network 1 through the private communication system, and also has direct access to the public network 1.
A portable radio telephone equipment which is carried by a customer of the department store is constructed as in the portable radio telephone equipment 50. However, a customer's private protocol processing section 11 is used for, for example, communication between a primary telephone and a secondary telephone for domestic use. Thus, the customer's portable radio telephone equipment does not allow the access to the private communication system of the department store.
FIG. 3 is a functional block diagram showing a configuration of the radio base station 40. In FIG. 3, reference numeral 21 means a transmitting/receiving section which is connected to the transmitting/receiving section 15 of the portable or mobile radio telephone equipment 50 by radio, and 22 means a private control channel controlling section to control a private control channel. Reference numeral 23 means a private protocol processing section to process a private protocol, and 24 means a line processing section to perform connection to the PBX 30. The radio base station 40 does not include a public protocol processing section to process a public protocol.
On the other hand, the radio base station 40B directly connected to the public network 1, includes a public protocol processing section, but does not include a private protocol processing section.
FIG. 4 is a functional block diagram showing a configuration of the PBX 30. In FIG. 4, reference numeral 31 means a line interface connected to the radio base stations 4, and 32 means a system discriminating function section to discriminate a call of the portable or mobile radio telephone equipment 50 that belongs to an own system from a call of the portable or mobile radio telephone equipment that belongs to another system or the domestic portable or mobile radio telephone equipment. Reference numeral 33 means a private protocol control section to control transmission from the system discriminating function section 32 in case it is decided by the system discriminating function section 32 that the call is sent from the own system. Reference numeral 34 is a transmission stopping section to stop the transmission from the system discriminating function section 32 in case it is decided by the system discriminating function section 32 that the call is sent from another system. Further, reference numeral 35 means a network interface to connect the private protocol control section 33 to the public network 1.
A description will now be given of the operation. The requests for connection to the public network 1 from the respective portable or mobile radio telephone equipment 50 are processed in the respective public protocol processing sections 13. The public control channel controlling section 14 permits direct access to the public network through the transmitting/receiving section 15 in response to the request for connection. Therefore, authentication and accounting at the time are performed in the public protocol processing section of the portable or mobile radio telephone equipment 50.
On the other hand, the requests for connection to the private mobile communication system from the respective portable or mobile radio telephone equipment 50 are processed in the respective private protocol processing sections 11, and are sent to the respective private control channel controlling sections 12. Accordingly, through the transmitting/receiving section, the private control channel controlling sections 12 allow access to the radio base station 40 in charge of a zone in which the portable or mobile radio telephone equipment 50 exists. In the radio base station 40, the request for connection is received by the transmitting/receiving section 21, and is sent to the private protocol processing section 23 through the private control channel controlling section 22. Further, the request for connection is sent out to the PBX 30 through the line processing section 24.
As an example, FIG. 5 shows process in the public protocol processing section 13. The process is disclosed in FIG. 4.4.3.8.1 which is shown in Second Generation Wireless Telephone System, 1st Ed. Standard, RCR STD-28 (hereinafter referred to as RCR STD-28) published by Research and Development Center for Radio Systems. In FIG. 5, a sequence designated by CC, RT, and MM in a batch transmission controlling sequence is shown. The private protocol processing section 11 also requires the same process as that in the public protocol processing section 13.
FIG. 6 shows formats of call signals shown in FIG. 4.2.20 of RCR STD-28. As shown in FIG. 6, the format in the private system is significantly different from the format in the public system. The private control channel controlling sections 12 incorporates a calling station identification code and a called station identification code in the private system shown in FIGS. 6(a) and 6(b) into a control physical slot. The public control channel controlling section 14 similarly incorporates a calling station identification code and a called station identification code in the public system shown in FIGS. 6(c) and 6(d) into the control physical slot.
The PBX 30 has a function to enable access to only the private control channel in response to the call out and the call in from the private mobile communication system. The request for connection from the respective radio base stations 40 is received by the line interface 31, and is sent to the system discriminating function section 32. The system discriminating function section 32 discriminates whether the request for connection is sent from the portable or mobile radio telephone equipment 50 which is registered in the private system or the request for connection is sent from a portable or mobile radio telephone equipment in another private mobile communication system or from a domestic portable or mobile radio telephone equipment. As a result, in case it is decided that the request for connection is sent from a portable or mobile radio telephone equipment which is not registered in the private system, the transmission stopping section 34 stops transmission in response to the request for connection.
Therefore, when the customer in the department store intends to have access to the PBX 30 by using the portable radio telephone equipment which is carried by the customer, the transmission is stopped.
FIG. 7 shows a frequency map at this time. In FIG. 7, the ordinate axis means each frequency at which each slot is positioned, and the transverse axis means each purpose for which each slot is used, i.e., whether each slot is used for private purpose or for public purpose. Thus, for example, a control physical slot positioned between frequencies f1 (MHZ) and f2 (MHZ) corresponds to frequency which is set by the private control channel controlling section 12, and a control physical slot positioned between frequencies f3 (MHZ) and f4 (MHZ) corresponds to frequency which is similarly set by the public control channel controlling section 14.
On the other hand, in case the system discriminating function section 32 determines that the request for connection is sent from the portable or mobile radio telephone equipment 50 which is registered in the private system, the PBX performs connection in a system when the request for connection is a request for connection in the system. Otherwise, when the request for connection is a request for public connection, the private protocol control section 33 in the PBX 30 transmits a signal to the public network 1 through the network interface 35. When the signal is transmitted to the public network 1, the PBX 30 itself performs the authentication and accounting.
Techniques relevant to the conventional mobile communication system as described before are disclosed in, for example, Japanese Patent Application Laid-Open No. 2-192329.
The conventional private mobile communication system is provided as set forth above. Consequently, the portable or mobile radio telephone 50 that belongs to the system allows the access to the public network 1 through the PBX 30, and also enables the direct access to the public network 1. However, the portable or mobile radio telephone equipment which does not belong to the system does not permit the access to the public network 1 through the PBX 30.
That is, in order to provide the access to the public network 1 by using the portable or mobile radio telephone equipment which does not belong to the system, the direct access is the only practical way. Therefore, in case there is no radio base station in the public network 1 in the vicinity of the portable or mobile radio telephone equipment, the portable or mobile radio telephone equipment does not permit the access to the public network 1 even if the portable or mobile radio telephone equipment is in a condition to enable the access to the radio base station 40 in the private mobile communication system.
For example, in case the customer comes to the department store with a portable radio telephone equipment, the equipment does not permit the access to the public network 1 unless the equipment allows the access to the radio base station in the public network 1.